Radiosignaling system



E. F. W. ALEXANDEBSON.

RADIOSIGNAUNG SYSTEM.

Curr-emf, Y

Fr'equehc APPLICATION FILED OCT. 16. I917.

Patented N 0v. 4,11919.

Inventor: Ernst F'. filexderson,

ERNST F. W. ALEXANDERSON, OF

SCI-IENECTADY, NEW YORK,

. ANT on.

ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

RADIOSIGNALING SYSTEM.

Specification of Letters Patent.

Patented Nov. 4, 1919.

Application filed October 16, 1917. Serial No.196,95 8.

- My present invention relates to radio signaling systems and particularly to means for transmitting radio signals by the use of continuous radio frequency currents.

In my prior applications, Serial No.

- 43,725, filed August 5, 1915; Serial No.

92,152, filed April 19, 1916, and Serial No. 189,495, filed September 1, 1917, I have described systems for transmitting radio signals by producing amplitude pulsationsin a continuous radio frequency current suppliedto a radiating antenna system. I have in these applications shown that a cont1nuous radio frequency current of a fundamental frequency having amplitude pulsations may be resolved into three components, one of the fundamental frequency, one which has a frequency equal to the fundamental plus the frequency of the amplitude pulsations and a third of which has a frequency equal to the fundamental minus the frequency of the amplitude pulsations.

One of the objects of my invention is to provide a transmitting system which will transmit signals of the class described most efficiently.

In attaining this object I tune the radiating system in such a way that instead of being in resonance for the fundamental frequency it is in resonance for one of the other frequencies into which the composite wave may be resolved, preferably the. component having a frequency equal to the fundamental plus the frequency of theamplitude pulsations. In the last named application I have shown how amplitude pulsations of several different fre uencies may be produced simultaneously. n this case the antenna will preferably be tuned for a frequency equal to the fundamental plus the highest frequency of amplitude pulsation employed. In case the amplitude pulsations to be transmitted are produced by means of speech currents the antenna will preferably be tuned for a frequency equalto the fundamental plus the characteristic speech frequency which may be taken as from 800 to 1000 cycles.

- A radiating system operated in this way has the disadvantage that the fundamental wave is out of tune with the antenna and in case an alternator is used as a current SOIH'C) the load on the alternator will have a lar; component of wattless current.

A further object of my invention is to overcome the above mentioned disadvantage and this object may be attained by tuning the alternator circuit for thefundamental frequency. 1

The novel features which I believe to characteristic of my invention are set forth with particularity in the appended claims.

-The invention itself, however, both as to its organizationand method of operation, together with further-objects and advantage: thereof will best be understood by reference to the following description taken in connection with the accompanying drawing-in which Figure 1 shows diagrammatically a circuit connection which may be employed in carrying my invention into effect and Fig. 2 shows by means of curves the relations between altcrnator currents and antenna current when the system operates in accordance with my invention.

In the system indicated in Fig. 1 the antenna 1 is supplied with radio frequency current from the high frequency alternator 2, the terminals of which are connected to the points 3 and 4 of the antenna circuit. Connected in shunt to the alternator terminals is a magnetic amplifier 5 comprising a suitable core (3 of magnetic material and two windings 7 and 8 as indicated. These Windingsare so arranged that the high frequency current supplied from the alternator flows through the two windings 7 and 8 in parallel and that the flux produced by this current flows in opposite directions through the portions 9 and 10 of the core' 6.

In order to adjust the magnetization of the core 6 to a point at which the device will operate most efficiently, direct current may be supplied to the windings 7 and 8 from a generator 11 at the points 12 and 13, the strength of the current being regulated by 'a variable resistance 14. This current will flow through the-two windings in series. The points'12 and 13 are at the same potential with respect to the high frequency source and hence there is no tendency for high frequency current to flow through the Circuit which supplies direct' current to windings 7 and 8. The condensers 15 and 16 which are in series with each of the windings 7 and 8 prevent the short circuiting of the direct current circuit.

In order to produce amplitude pulsations in the antenna current with the arrangement thus far described, it is only necessary to vary the controlling current in windings 7 and 8. I have in the present case illustrated one convenient method of simultaneously producing amplitude pulsations of three different frequencies for the transmission of three different messages. The alternators 17, 18 and 19 are designed to produce currents of three different frequencies lower than that of alternator 2, all of which if desired may be within the range of audibility. For example, alternator 17 may give 800 cycles, alternator 18, 700 cycles, and alternator 19, 000 cycles. Poles 20, 21 and 22 of these alternators are connected directly to the circuit which supplies direct current to windings 7 and 8 and poles 23, 21 and 25 are connected to that circuit through keys 2G, '27 and 28, respectively. If the alternators have the frequencies mentioned, when key 26 is closed 800 cycle current will be supplied to windings .7 and 8 and a message transmitted by key 26 will be transmitted by means of amplitude pulsations having a frequency of 800. Similarly a second message may be transmitted simultaneously by key 27 by means of amplitude pulsations having a frequency of 700, and a third message may be transmitted by key 28 by means of amplitude pulsations having a frequency of 600. The operation of the control apparatus may be improved by the use of a condenser 29 in series with wind. ings 7 and 8, and so adjusted that the circuit in which it is included becomes resonant when the antenna current is a minimum.

I have shown in my prior applications referred to above that a wave of fundamental frequency having amplitude,pulsations may be resoled into three components and that if any two of these components are transmitted they may be combined at the receiving station to produce a wave of fundamental frequency with amplitude pulsations of the frequency produced at therecciving station. If, however, the antenna is tuned to the fundamental frequency the component corresponding to that frequency will be transmitted with a maximum amplitude and the amplitude of the other components will be so low that the amplitude pulsations produced at the receiving station by the combination of the components will be of small magnitude in comparison with the total ci'lrrent received. This diszulvantage may be overcon'ie by adjusting the tuning of the antenna circuit by means of the usual variable iinluctance 30 so that it is resonant for a frequency equal to the highest quency component of the amplitude pulsa tions. For example, 1n the case described in connection with Fig. 1 the antenna c1reuit may be tuned to a frequency equal to.

the fundamental plus 800. Then assuming that the dotted curve of Fig. 2 represents the tuning curve of the antenna, the component which has a frequency equal to the fundamental plus 800 may fall at the polnt A, the component which has a frequency equal to the fundamental plus 7 00 may fall at the point B, the component which has a frequency equal to the fundamental plus 600 may fall at the point C and the component having a frequency equal to the fun damental may fall at the point D.

In case the amplitude pulsations are produced by means of speech currents, it will be desirable to tune the antenna circuit to a frequency equal to that of the fundamental wave plus approximately 1000 cycles as the representative higher harmonics of the Voice have a frequency of from 800 to 1000 cycles. The distortion of speech over telephone lines has been largely overcome by tuning the lines for this frequency so that the amplification of the higher harmonics by tuning compensates the tendency which the line would otherwise have to suppress the liarmonics. By tuning the antenna for a frequency 1000 cycles greater than that of the fundamental wave employed, a result may be attained which is'equivalent to tuning a wire line for the higher harmonics of the voice.

It will be apparent, however, that if the antenna is tuned for a frequency higher than that of the fundamental wave, the alternator can not deliver as much power as it couldif the antenna was resonant to the fundamental frequency. The antenna load on the alternator becomes equivalent to a condenser load and the alternator will work at a very low power factor. One apparent way to overcome this disadvantage would be to neutralize the capacity load of the antenna by means of inductance. If this were done, however, inthe most obvious way, the desired result would not be secured because the antenna tuning would be phanged so that it would be in resonance with the alternator frequency. I have found-that the desired correction may be obtained by tuning the alternator circuit. The alternator will deliver its maximum output when the inductive reactance of its circuit is balanced by an equal capacity reactance. in the present case this may be accomplished by means of a variable condenser 31 in the alternator circuit which is so adjusted as to neutralize the internal inductance of the alternator. Across the terminals of the tuned alternator circuit is placed an inductance 32 whichis so adjusted that it neutralizes the wattless componem of the 311- tenna current which has the character of a condenser load. This inductanceis so chosen that the resulting resonant voltage of the antenna across the terminals of the alternator circuit is equal to the energy voltage which the alternator can deliver at unity power factor. If this adjustment is properly made the alternator will deliver current at unity power factor to the oscillating antenna circuit although the antenna is not in tune with the alternator. The shunt inductance when used this way will have practically no effect upon the antenna tuning but it will neutralize the capacity load of the alternator and allow itto deliver energy at substantially unity power factor. The effect of this arrangement is indicated in Fig. 2. An'inspcction of this figure Wlll show that although the antenna is not resonant to the alternator frequency, the alternator will deliver its maximum current when the antenna current is a maximum.

Whilel have illustrated and described a single embodiment of my invention, 1 do not wish to be limited to the specific circuit arrangement shown, as itwill be apparent that many variations may be made in-the circuit arrangements and the apparatus employed without departing from the scope of my invention as set forth in the appended,

claims.

lVhat I claim as new and desireto secure by Letters Patent of the United States, is,

1. A system for transmitting radio slgnals comprising a source of continuous radio frequency current of a definite frequency, means for producing amplitude pulsations in the current derived from said source and a radiating antenna supplied with current from said source and tuned for resonance at a frequency equal to that of the source plus the most important frequency of the amplitude pulsations.

2. The method of transmitting radio sig nals which consists in producing amplitude pulsations corresponding to the signals to be transmitted in a continuous radio frequency current and supplying the current having amplitude pulsations therein, to a radiating antenna system which is resonant to a frequency equal to the frequency of the source plus the frequency of the most important amplitude pulsations.

3. A system for transmitting radio signals comprising a source of continuous radio frequency current, a radiating antenna system supplied with energy from said source and tuned for resonance to a frequency which is materially different from that of the source and means for adjusting the sys tem in such a way that the current supplied by the source is substantially in phase with the electromotive force.

4. A system for transmitting radio si nals comprising a source of continuous radio frequency current, a radiating antenna system which is resonant to a frequency which is materially different from that of the source and a circuit for supplying energy from said source to said antenna, the combined energy supply circuit and antenna being resonant to the frequencyof said source.

5. A system for transmitting radio signals bomprising a source of continuous radio frequency current, a radiating antenna, aloral circuit for supplying current from said source to said antenna, and means for producing amplitude pulsations in the current in said antenna, said local circuit being resonant to the frequency of the source, and said antenna being resonant to a frequency equal to the frequency of the source plus that of the most important amplitude pulsations of the current therein.

6. The combination in a system for transmitting signals by means of high frequency continuous waves having amplitude pulsations, of a resonant transmitting circuit, a source of continuous high frequency current adapted to supply energy to said transmitting circuit, and means for tuning the circuit supplied by said source so that the current and voltage supplied by said source are in phase at a different frequency from the resonant frequency of the transmitting circuit. 7. The combination in a signaling system of a source of high frequency alternating current, a signal transmitting circuit which is resonant to a frequency which is difierent from that of the source, means for producing amplitude pulsations corresponding to signals in the current supplied from said sources of said signal transmittingcircuit, and means for tuning the system in such a way that the current suppliedby the source is substantially in phase with the electromotive force.

8. The combination in a signaling system 'of a source of high frequency alternating current, a signal transmitting circuit which is resonant to a frequency diiferent from that of said source, a local circuit connecting said source to said signal transmitting circuit which is resonant to the frequency of said source, and a reactance in shunt to said local circuit for balancing the reactance of the signal transmitting circuit so that the current supplied by the source will be substantially in phase with the electromotive force.

9. The combination in a signaling system of a high frequency alternator, a signal transmitting circuit which is resonant to a frequency which is difi'erent from. that of the current supplied by said alternator, a local circuit for supplying current from. said alternator to said signal transmitting circuit, a capacity in said local circuit for neutralizing the internal inductance of the alternator, and reactance 1n shunt to said local circuit and said signal transmitting circuit for balancing the reactance of the latter so that the current supplied by the source Will be substantially in phase with the electromotive force.

10. The combination in a signalingsystem of a source of continuous radio frequency current of a definite frequency, means for producing amplitude pulsations in the current derived from said source a signal transmitting circuit supplied with current from said source and tuned for mitting circuit for neutralizing the capacity reactance of the transmitting circuit so that the current supplied by the source will be substantially in phase with the elec- 20 tromotive force,

In Witness whereof, I have hereunto set mu hand this 15th day of October, 1917.

ERNST F. W. ALEXANDERSON. 

